1. Field of the Invention
This invention relates to fastener setting machines. More specifically, the invention relates to a fastener setting machine in which the upper receiver for the fastener part comprises spreadable jaws pivotally mounted in an assembly which descends toward the setting locus as the punch comes down. For safety reasons, the upper position of the receiver is closely spaced above the guide plate.
2. Description of Related Art
The prior art includes a number of receivers for setting machines. An example is shown in the U.S. Pat. No. 1,632,374 to A. F. Havener. In this patent fixed jaws hold the part until the upper punch comes down driving the jaws open and forcing the part downward to the setting locus.
In another U.S. Pat. No. 434,214 which issued Aug. 12, 1890 to J. L. Thompson rivet-holding shoulders are in a moveable receiver. A punch comes down forcing the shoulders to give way taking the part with it.
Spencer U.S. Pat. No. 277,369 shows a rivet setting machine in which the jaws stay at a fixed level and serve as a receiver for the upper part. The punch comes down, engages the part and forces it to open the jaws, driving the part on down to the setting locus.
In all of the above receiver arrangements there is a definite safety hazard in that the distance between the level of the jaws and the setting locus is considerable and it is possible for the operator to have the punch descend before he can withdraw his fingers.
More recently the emphasis has been on safety. A typical arrangement is as shown in the U.S. Pat. No. 4,343,423 to O. S. Sauermilch which issued Aug. 10, 1982 and in which the guard descends before the punch. If the guard is blocked from fully descending because the operator's fingers are in the way, the stroke of the punch itself is blocked until the obstacle is removed.
A more recent reference is U.S. Pat. No. 4,454,650 to B. R. Silver. The upper tool receiver is installed in an oversize head which is stationarily mounted on the setting machine so that its lower end is closely adjacent the setting site. The head includes jaws which temporarily receive the fastener part. A punch then comes down through the jaws grabbing the part and holding it with special retaining means, then continuing its travel to the setting site. In Silver the intention is that an operator will not be able to get his fingers between the bottom of the oversize head and the setting site.
The Silver patent has required that the punch have retaining means to hold the fastener part on its brief and precipitous downward travel. Such retaining means have not always been reliable. In addition, because the head is stationarily mounted on the setting machine, the lower receiver is not readily accessible.